Re: [Xen-devel] [PATCH 02/16] x86: fix: make atomic_read() param const

[Corneliu ZUZU <czuzu@xxxxxxxxxxxxxxx>]

On 7/12/2016 12:42 PM, Andrew Cooper wrote:
> On 12/07/16 06:11, Corneliu ZUZU wrote:
> > Hi Andrew,
> >
> > On 7/11/2016 6:18 PM, Andrew Cooper wrote:
> > > On 09/07/16 05:12, Corneliu ZUZU wrote:
> > > > This wouldn't let me make a param of a function that used
> > > > atomic_read() const.
> > > >
> > > > Signed-off-by: Corneliu ZUZU <czuzu@xxxxxxxxxxxxxxx>
> > > This is a good improvement, but you must make an identical adjustment to
> > > the arm code, otherwise you will end up with subtle build failures.
> > Right, didn't even realize it was X86-specific.
> It isn't x86 specific.  (Which is what I presume you meant to say.)
Heh, yes, depends how you look at it, I was referring precisely to (the 
implementation of) the function I've modified (which was X86-specific, 
called from common, which meant there's an ARM one as well).
> > > If you are really feeling up to it, having a common xen/atomic.h with
> > >
> > > typedef struct { int counter; } atomic_t;
> > > #define ATOMIC_INIT(i) { (i) }
> > >
> > > and some prototypes such as:
> > >
> > > static inline int atomic_read(const atomic_t *v);
> > >
> > > would be great, but this looks like it has the possibility to turn into
> > > a rats nest.  If it does, then just doubling up this code for arm is ok.
> > >
> > > ~Andrew
> > Yes, that might be more complicated than we expect and I don't know if
> > making code such as this common would be a good idea, usually these
> > functions are always architecture-specific.
> I only suggested making the prototype common, not the implementation.
> As such, the issue you accidentally introduced would become a hard build
> failure on affected architectures, rather than a subtle build failure in
> common code at some point in the future.
>
> ~Andrew
Oh, I see, good idea, I've just tested it and it works, what did you 
have in mind when you said it could cause problems?
Zuzu C.

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